52 Wage r. — The Nucleolus and Nuclear Division 
nucleolus becomes reduced in size or disappears, as in the guard-cells 
of stomata, in the gland-cells of Chironomus , and in the male sexual cells 
of plants and animals. In all such cases the nucleolar substance probably 
migrates into the nuclear thread, and remains there so long as the nucleus 
is in an active state, to be stored up in the nucleolus again when the 
activity ceases. Farmer and Williams 1 and Strasburger 2 have shown, for 
example, that the sperm-nucleus of Fucus is very rich in chromatin, and 
at the time of fusion with the ovum-nucleus exhibits a network-structure 
but no nucleolus. After fusion, a second large nucleolus appears in the 
ovum-nucleus, apparently derived from the chromatin of the sperm-nucleus. 
Here we might suppose that the male nucleus, on its entry into the 
quiescent female nucleus, loses its intense activity, and that the 
chromatin-substance therefore becomes accumulated in the form of a 
nucleolus. 
So also Ikeda 3 has shown, in his observations on the nutritive function 
of the antipodals in Tricyrtis hirta , that during their stage of metabolic 
activity the nucleolus decreases in size, whilst the original scanty chromatin- 
network shows an extraordinary increase of chromatin, which becomes 
variously aggregated within the nucleus. 
It may be objected that chromatin-nucleoli, such as we have in Phaseolus , 
are only masses of chromatin-substance, and ought not to be confounded 
with those nucleoli which do not give a chromatin-reaction. There certainly 
appear to be two distinct types of nucleolus in some animal-cells, and it is 
possible that the same may exist in plant-cells also ; but the evidence 
before us as to their chemical constitution, and staining, and other reactions, 
is not at present sufficient to differentiate them into two distinct categories 4 . 
We must rely mainly upon their morphological behaviour, and so far this 
has not produced much evidence of such a differentiation. As Montgomery 
suggests, it may be that all these bodies, which some observers are inclined 
to regard as fundamentally different structures, may be regarded as ‘ true 
nucleoli of a different chemical nature 5 .’ 
In conclusion, it appears to me, from a careful consideration of the facts 
as presented to us by various observers, that the following statements 
are probably justified as a summary of our present knowledge of plant- 
nucleoli : — 
(i) That the rounded bodies present in nearly all plant-nuclei, which 
1 Fertilization of Fucus, Phil. Trans., 1898. 
2 Kerntheilung und Befruchtung bei Fucus, Pringsh., Jahrb. f. wiss. Bot., xxx, 1897, p. 364. 
3 Studies in the Physiological Functions of Antipodals and Related Phenomena of Fertilization 
in Liliaceae : (1) Tricyrtis hirta, Reprint from Bulletin, Coll, of Agriculture, Tokyo Imperial Univ., 
v, 1902, p. 41. 
4 Cf. Fischer, Fixirung, Farbung und Bau des Protoplasmas, Jena, 1899, pp. 98-102, and 
Mann, Physiological Histology, Oxford, 1902. 
5 Wood’s Holl. Bio. Lectures, 1898. 
